1. Field of the Invention
The present invention relates generally to an actively controlled suspension system for an automotive vehicle for controlling suspension characteristics for achieving riding comfort and/or vehicular driving stability depending upon the vehicle driving condition. More specifically, the invention relates to an actively controlled automotive suspension system which can improve suspension control characteristics upon starting-up of an automotive engine.
2. Description of the Background Art
The U.S. Pat. No. 4,702,490, issued on Oct. 27, 1987, to Hirotsugu YAMAGUCHI et al., and assigned to the common assignee to the present invention, discloses an actively or positively controlled automotive suspension system which includes a hydraulic cylinder for generating a variable damping force against relative motion of a vehicular suspension member and a vehicle body in bounding and rebounding directions for adjusting suspension characteristics and adjusting vehicle body attitude.
Similar type actively controlled suspension systems have been disclosed in the co-pending U.S. patent application Ser. No. 060,911, filed on June 12, 1987, and assigned to the common assignee of the present invention, and, European Patent First Publications Nos. 02 49 246 and 02 49 209 respectively corresponding to co-pending U.S. patent applications Ser. Nos. 061,368 (filed on June 15, 1987) and 059,888, filed on June 9, 1987, both of which have been assigned to the common assignee to the present invention. These three inventions include features of anti-rolling and/or anti-pitching suspension control for adjusting damping characteristics at respective vehicular wheel for suppressing vehicular rolling motion.
In order to perform anti rolling and/or anti-pitching suspension control, various suspension control parameters can be used for detecting the vehicular attitude change in rolling and/or pitching directions. Among various vehicular rolling and/or pitching representative parameters, an acceleration exerted on the vehicular body in lateral and/or longitudinal directions is one typical parameter to be used for anti-rolling and/or anti-pitching suspension control. In such case, vehicular body vibration caused by engine vibration which may be induced while the engine is driven in an unstable condition, will affect acceleration dependent attitude control. For example, when the engine starts or while the engine is in a cranking condition, substantial vibration is created. The engine vibration is transferred to the vehicular body and thus detected by an acceleration sensor which is provided for detecting lateral and/or longitudinal acceleration exerted on the vehicular body. This produces an erroneous detection of an attitude change of the vehicular body, despite the vehicle body not changing attitude. Mis-detection of a vehicular attitude change results in erroneous suspension control which causes an uncomfortable attitude change in the vehicular body.